bogs down on full throttle

[Muzza]

hi folks still having probs i rebuilt the carb and its now strating and will idle but when you give it full throttle it bogs down and wont rev!! any ideas?? fuel pressure all 100% new filter im lost..

[Chunk]

spark/plugs?

[s3irios]

Air leaks, If you're doing full throttle fast maybe wrongly adjusted idle, meaning too rich or too lean, but my bet is still in air leaks somewhere. After that, check dizzy cap-plugs-spark cables.

[Scoff]

does it rev if you open the throttle slowly ? If it only dies when you open the throttle fast then look at the pump jet and it's linkage. If it doesn't rev above 2000rpm or so no matter how slow you open the throttle then there might be a fundimental problem with the main jet, air corrector, emulsion tube, path to secondary venturi or something like that. A carb will idle fine on the idle/progression circuit but it needs the other stuff once you open the throttle more than a few degrees.

[Muzza]

spark/plugs?


new plugs in her new dizzy cap and drive and leads.

[Muzza]

does it rev if you open the throttle slowly ? If it only dies when you open the throttle fast then look at the pump jet and it's linkage. If it doesn't rev above 2000rpm or so no matter how slow you open the throttle then there might be a fundimental problem with the main jet, air corrector, emulsion tube, path to secondary venturi or something like that. A carb will idle fine on the idle/progression circuit but it needs the other stuff once you open the throttle more than a few degrees.


yeah if you open throttle slowly there is no prob you can drive it not a prob like that but when you give it some it just starts poping and baging. how would i find out if any of them things you listed are faulty?? carbs are my worst nightmare.

[LiamR]

Have you got an afr gauge fitted?? This will tell u if your fuelling is correct.

It sounds like a possible air leak to me. Spray a bit of wd40 around the carb and see if the engine note changes? This would indicate an air leak.

It's what happened on mine. The green seals around the throttle shaft were not sealing and letting air in.

[Muzza]

Have you got an afr gauge fitted?? This will tell u if your fuelling is correct.

It sounds like a possible air leak to me. Spray a bit of wd40 around the carb and see if the engine note changes? This would indicate an air leak.

It's what happened on mine. The green seals around the throttle shaft were not sealing and letting air in.


No sadly no afr guage fitted need to get one! Was messing about a bit there and if I take the vacuum pipe off the back of the carb that is connected to the crankcase breather and block it the car cuts out is that normal??

[Tony Walker]

no should be fine with it blocked.

[Muzza]

no should be fine with it blocked.


See that's what I thought I will block this off and set the carb up again and see what happens! Thanks

[Kris M]

My cup car held back like this before...if its popping and banking and holding back, check your fuel pressure at the carb. Should be at least 4psi above boost pressure. If not it could be fuel pump, blocked filter / sender. Pressure reg

[Kingscott]

check the pressure reg.

I had this a few years ago and fitted a FSE.

[Muzza]

My cup car held back like this before...if its popping and banking and holding back, check your fuel pressure at the carb. Should be at least 4psi above boost pressure. If not it could be fuel pump, blocked filter / sender. Pressure reg

Have checked this this and the new pump and filter about 100 mile ago!

[Nottswoody]

Have checked this this and the new pump and filter about 100 mile ago!

I had something similar I bought a fuel pump from euro parts an it was a gt pump and when then turbo pulled it held back and popped turned out not enough pressure got my money back and a very nice member sold me a phase 1 pump and all was good again..